1. Field of the Invention
The present invention relates to resin compositions having high solids contents useful as wet strength resins and creping compositions.
2. Discussion of Background Information
In the papermaking industry, it is common to attempt to optimize papermaking compositions in order to provide specific functional properties as efficiently and economically as possible. Wet strength resins are a common additive to papermaking compositions. These materials act to provide strength to wet paper and are used in, among other paper products, paper towel and packaging. Among other uses, they are also useful as creping adhesives. Wet strength resins may be added during paper production to bind the cellulose fibers together, and to enhance the strength of the paper produced so that the paper does not fall apart when used under wet conditions. Such resins may be added to pulp and formed paper.
Commonly available wet strength resins are marketed under the brand name KYMEME(copyright) by Hercules Incorporated, Wilmington, Del. Attempts have been made to optimize such wet strength resins. Aqueous dispersions of such resins, having relatively high solids content, are desirable.
KYMENE 557H (copyright) has long been a benchmark for strength additives in the papermaking industry. It is based on the reaction product of poly(adipic acid-co-diethylenetriamine) and epichlorohydrin. An excess of epichlorohydrin is used to control the rate of cross-linking during the manufacturing process and to aid in storage stability. Such compositions, and processes for their manufacture are disclosed in U.S. Pat. Nos. 2,926,116 and 2,926,154, both to KEIM and commonly assigned to Hercules Incorporated. These patents are incorporated by reference as though set forth in full herein.
Originally supplied as a 10% aqueous solution, the solids of such compositions were eventually raised to about 12.5%. A number of other wet strength resins were developed with improvements based on this initial chemistry. Examples of such improvements are disclosed in U.S. patent application Ser. No. 09/363,224 filed Jul. 30, 1999 and now abandoned commonly assigned to Hercules Incorporated, and hereby incorporated by reference as though set forth in full herein; U.S. Pat. No. 5,614,597 to BOWER, commonly assigned to Hercules Incorporated, and hereby incorporated by reference as though set forth in full herein, and U.S. Pat. Nos. 5,644,021 and 5,668,246, both to MASLANKA, also commonly assigned to Hercules Incorporated, and incorporated by reference as though set forth in full herein. Illustrative of such products are KYMENE 557LX(copyright) (which include advantages of reduced epichlorohydrin by-products); KYMENE ULX (which include advantages of very low levels of epichlorohydrin by-products) and KYMENE PLUS(copyright) (which exhibit 30% solids).
The provision of effective high solids resins has been a longstanding goal in the industry, both as a benefit to suppliers as well as to paper manufacturers. It is believed that KYMENE PLUS(copyright) is the highest solids polyamide-based product, at 30% solids.
It is particularly desirable to provide a resin that provides a high solids content, while also being equivalent to the KYMEME(copyright) resins.
It is also desirable to provide a resin that would offer a significant improvement in wet strength over, for example, KYMEME(copyright) 557H wet strength resin-carboxymethyl cellulose (CMC) combinations, that would have low epihalohydrin residual levels and that would be economically repulpable. This combination of a polyamidoamine-epihalohydrin resin and CMC generates a coacervate (semi-gelatinous mass) that improves resin retention and improves overall bonding of the resin with the cellulose fibers.
Further, it is desirable to provide such a resin that is also useful as a creping adhesive.
The invention provides polyamidoamine resins. The invention also provides aqueous dispersions of such resins, and, additionally, aqueous dispersions of wet strength resins which have high solids contents and favorable wet strengthening and/or adhesion properties. Compositions of the invention are useful as wet strength resins and as creping adhesives.
The resins of the invention provide advantages of ease of production
The resins of the invention also provide advantages of high solids contents and storage stability.
In preferred embodiments, the resins of the invention are based on water-soluble polyamidoamine resins having the structure(s) set forth in Formula I, below: 
wherein:
R1 is a substituted or unsubstituted hydrocarbon group;
R2 is a substituted or unsubstituted hydrocarbon group;
R3 is a substituted or unsubstituted hydrocarbon group; and
Z is halogen selected from F, Cl, Br and I, and combinations thereof.
The invention also relates to resin compositions containing such resins, and to methods of treating paper, paper products and cellulosic products and making paper products and cellulosic products using such resins and resin compositions.
The invention also comprises methods of preparing such resins. Such methods comprise:
reacting at least one polyamide having the structure 
xe2x80x83wherein
R1, R2, and R3 are as defined above;
with at least one ammonium halide compound and at least one epihalohydrin compound having the structures: 
xe2x80x83wherein
Z is as defined above.
The invention also provides water-soluble polyamides prepared from such reactants.
The invention provides methods of increasing the wet strength of a cellulosic product comprising cellulose fibers comprising adding to one of the cellulose product or fibers such a water-soluble polyamidoamine resin.
The invention provides methods of creping a cellulosic product comprising cellulose fibers comprising adding to one of the cellulose product or fibers such a water-soluble polyamidoamine resin.
The invention provides a cellulosic product prepared by the foregoing methods.
In any of the foregoing, R1 may be alkyl of from 1-6 C atoms, more preferably alkyl of 3-5 C atoms, more preferably 4 C atoms; R2 may be alkyl of from 2-4 C atoms, more preferably alkyl of 2 C atoms; R3 may be alkyl of from 2-4 C atoms, more preferably alkyl of 2 C atoms; x is from about 10 to about 30 mole % 15, more preferably about 25 mole %; more preferably about 20 mole %, and y is from about 70 to about 90 mole %, more preferably about 75 to about 85 mole %, more preferably about 80 mole %.
In any of the foregoing, the aqueous resin composition may preferably have a solids content of at least about 35%, more preferably about 50%, more preferably about 54%, more preferably about 55%.
In any of the foregoing, x may preferably be Cl.
The present invention is related to the discovery that compounds of Formula I 
provide wet strength resins and creping adhesives which exhibit desirable properties, such as a high solids content when the resins are in the form of an aqueous dispersion. The invention is also directed to compounds of Formula (I) per se.
The invention provides significant advantages of ease of production, and in preferred embodiments, a combination of ease of production, high solids content and storage stability, which combination is highly unexpected.
Preferably, compounds of Formula I are prepared by reacting compounds of the following Formulae (II), (III) and (IV): 
R1, R2 and R3 may be any substituted or unsubstituted hydrocarbon moiety of any length, which allows the compound of Formula (I) to be soluble in water. For example, R1, R2 and R3 can be straight or branched chain alkyl, alkenyl or alkynyl, cycloalkyl, cycloalkenyl, aromatic or other unsaturated cyclic compound, each of which may substituted or unsubstituted. In preferred embodiments, R1, is a substituted or unsubstituted hydrocarbon group selected from alkyl, alkenyl and alkynyl; and is preferably alkyl of from 1-6 C atoms, preferably 3-5 C atoms, more preferably 3-4 C atoms, and most preferably 4 C atoms; R2 is a substituted or unsubstituted hydrocarbon group selected from alkyl, alkenyl and alkynyl; and is preferably alkyl, of from 2-4 C atoms, most preferably 2 C atoms; and R3 is a hydrocarbon group selected from alkyl, alkenyl and alkynyl; and is preferably alkyl of from 2-4 C atoms, most preferably 2 C atoms.
In the compounds of Formula (I), x is from about 5 to about 45 mole %, more preferably from about 10 to about 40 mole %, more preferably from about 10 to about 30 mole %, most preferably from about 10 to about 20 mole %, preferably about 20 mole % for wet strength applications and about 10 mole % for creping adhesives; and
y is from about 55 to about 95 mole %, preferably from about 60-90 mole %, more preferably from about 70 to about 90 mole % and most preferably from about 80 to about 90 mole %, preferably about 80 mole % for wet strength applications, and about 90% for creping adhesives.
Preferably, for wet or dry strength resins, the ratio of the amount of compound of Formula (IV) and compound of Formula (II) employed should be kept as close to 1 as possible. Preferably, the mole ratio of compound IV to compound II is about 1, or less, based on mole %. Compound III is preferably employed in an amount of at least about 15 mol %, preferably at least about 25 mol %, based on the secondary amine of the compound of Formula II.
Additionally for wet or dry strength resins, the amount of compounds III and IV employed is such that the total molar amount of compound III+compound IV is stoichiometrically equal to the number of the secondary amine on the polyamide of formula II.
An exemplary composition is one employing about 20 mole % of a compound of Formula II, based on the molar amount of the compound of Formula III employed, and about 80 mole % of a compound of Formula IV, based on the molar amount of the compound of Formula III employed.
The epichlorohydrin:polyamine mole ratio, for applications both as wet strength resin and as a creping adhesive should be kept as close to 1:1 as possible, but lower ratios may be employed, on the order of 0.9:1 to about 0.95:1, as opposed to 1:1.
For utility as wet strength resins mole ratios of epichlorohydrin:quatemary amine (for example GTMAC) on the order of about 8:2 (4:1) may be employed. For utility as creping adhesives, epichlorohydrin:quatemaryamine (for example GTMAC) mole ratios on the order of 9:1 to about 9.5:1 may be employed.
In general, the utility of the compounds of the invention may be directed by varying pH of compositions containing the compounds. For use as a wet strength resin, the compounds of the invention may be activated with caustic.
Without wishing to be bound by theory, it is believed that both of the epoxide-based materials react with the secondary amine groups in the polyamidoamine backbone to provide cationic charge and aminochlorohydrin groups. The amount of each may be varied so as to vary the cationic charge versus potential azetidinium functionality.
Examples of compounds of Formula (II) include reaction products of dicarboxylic acids and alkylamines. Suitable dicarboxylic acids and alkylamines are set forth in U.S. Pat. No. 2,926,116 to KEIM, incorporated by reference herein above as well as specifically herein for its disclosure of such materials. Preferred compounds of Formula II include those wherein R1, R2 and R3 are as defined above; however, any compound in accordance with Formula II can be employed, as long as it is soluble in water. Dicarboxylic acids having from about 3 to about 10 carbon atoms are particularly preferred. Examples of such compounds include adipic acid, glutaric acid, malonic acid, sebacic acid, sebaric acid, etc. Examples of suitable alkylamines include polyalkylamines, and include iminobispropylamine, triethylenetetra-amine, tetraethylenepentamine, etc.
Examples of compounds of Formula (III) include epoxides or aminohalohydrins, preferably aminochlorohydrins, bearing quaternary ammonium groups.
Examples of compounds of Formula (IV) include epihalohydrins, such as epichlorohydrin, epibromohydrin and epi-iodohydrin.
In particularly preferred embodiments, resins of the invention are prepared by reacting a compound of Formula II comprising a polyamidoamine, with a compound of Formula III comprising a glycidyltrimethylammonium chloride (xe2x80x9cGTMACxe2x80x9d), activated with a base to form the quaternary ammonium and oxirane portions (the activation procedure being standard and well-known to those of ordinary skill in the art), and a compound of Formula IV comprising an epihalohydrin, for example, epichlorohydrin. R1, R2 and R3 can be varied beyond the preferred ranges given above, so long as the compounds are water soluble. Exemplary embodiments include those prepared by reacting starting materials including an amidoamine polymer at low temperature with glycidyltrimethylammonium chloride and epichlorohydrin. This provides at least some level of cationic charge for resin retention and aminochlorohydrin for potential functionality (azetidinium).
The reaction of compounds (II), (III) and (IV) can be conducted in any manner that produces compounds of Formula (I). Compounds (II), (III) and (IV) can be reacted together in a single reaction or in essentially a single reaction, such as, for example, by being added to the reaction vessel concurrently or essentially concurrently, or by adding compound (III) to compound (II) followed by immediately adding compound (IV) to the mixture upon completion of the addition of compound (III) to the mixture. Alternatively, compounds (II) and (III) can be reacted together first, followed by reacting the resultant compound with a compound of Formula (IV).
With either approach, the reaction with compound (IV) is preferably conducted at relatively low temperatures, preferably at temperatures slightly above room temperature. For example, reaction temperatures of, for example, up to about 35xc2x0 C. have been found to be suitable. Preferably, reaction temperatures in the range of about 25-35xc2x0 C. are utilized, more preferably up to about 33xc2x0 C., more preferably about 25xc2x0xe2x88x9230xc2x0 C. It will be understood that the temperature of the reaction mixture may be maintained in any suitable standard way, such as with a water jacket, ice bath or air. Preferably, the reaction is conducted with cooling, preferably, by ice, such as by an ice bath or a circulating cold water bath. The compounds of Formula IV are preferably added in such a manner as to control the temperature of the reaction mixture; preferably, dropwise.
In cases where compounds of Formulae (II) and (III) are reacted with each other first, this portion of the reaction can be conducted at higher temperatures. For example, the reaction can be conducted at temperatures of up to about 80xc2x0 C., or higher, preferably less than about 60xc2x0 C., more preferably less than about 50xc2x0 C. and more preferably less than about 45xc2x0 C., with one preferred range being from about 45xc2x0 C. to about 50xc2x0 C.
The reaction of compounds (II) and (III) is preferably conducted to completion, which has been found to take place in a time period of from about 30 to about 45 minutes.
When compound (IV) is added (either concurrently or after reaction of (II) and (III)), the reaction is preferably conducted to completion. Reaction times on the order of about 20-24 hrs have been found to be suitable, in accordance with the present invention. Longer reaction times may also be employed, as long as the reaction temperatures are maintained low, such as closer to room temperature. The term xe2x80x9cto completionxe2x80x9d is readily understood by those of ordinary skill in the art. Moreover, whether a reaction has been conducted to completion can also be determined by analysis of residual reactants, such as by gas chromatography.
The fact that the reaction of the invention can be conducted to completion provides a decided advantage in processing. Conventional reactions must be stopped prior to completion, because of the rise in viscosity, often resulting in gelling of the reaction mixture. In preferred embodiments, the reaction of the invention can be conducted to completion without gelling or substantially without gelling. This is so even under conditions of high solids.
Compounds of Formulae (II), (III), and IV) are preferably employed in amounts that result in a solids content in the reaction mix of from about 50% to about 55% solids, with the amounts of (II), (III), and (IV) relative to each other as set forth above.
The same general procedure as above may be employed throughout this series of resins and is otherwise identical to that used in the synthesis of KYMEME 557LX (disclosed in U.S. Pat. No. 5,614,597 to BOWER, which is hereby incorporated by reference as though set forth in full herein), except that the reaction is terminated after the alkylation step. At this point, the resin has cationic charge, minimum azetidinium and predominantly aminochlorohydrin groups (potential azetidinium or epoxide functionality). The resin, which has a low molecular weight due to the lack of cross-linking, can be stabilized with acid at approximately 50-55%, by weight solids.
Acid is added for stabilization to adjust the pH of the composition to a range of from about 2.5-4, preferably about 3-3.5. Any suitable acid may be employed, such as hydrochloric, sulfuric, nitric, formic, phosphoric and acetic acid. Hydrochloric acid is particularly preferred.
Glycidyltrimethylammonium chloride (GTMAC) (a particularly preferred compound of Formula III) may be generated from Quat 188(copyright) [N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride], available from Dow Chemical, Midland, Mich. via treatment with caustic prior to addition to the polyamide solution.
Preferred aqueous dispersions in accordance with the invention are those having a solids content of greater than 30%, preferably at least about 35%, more preferably at least about 50% and most preferably at least about 54% or at least about 55% based on the amount of resin, by weight, in comparison with the weight of the entire composition. Preferably, the solids content is measured by the following procedure: A sample of aqueous resin is first weighed and is then dried at a temperature of 150xc2x0 C., for a time period of about an hour or until constant weight, or until no water remains. The residue remaining is then weighed and the weight percent of the aqueous resin is then calculated based on the following: weight residue (resin)/weight of aqueous resin. The resulting value, expressed in weight percent, is the solids content of the (aqueous) resin.
In some embodiments, the present invention provides a resin having a total solids of 50-55% with an efficiency of about 90% that of KYMEME 557H. The solids content is 15-25% higher than existing resins. In addition, the resins of the invention exhibit excellent adhesion properties.
The resins of the invention may be activated in any suitable way; preferably, they are activated by treatment with caustic to convert halohydrins to epoxides. This allows the resin to crosslink with itself or cellulose fibers. Hydroxides are preferred materials for activation. Sodium hydroxide is particularly preferred. In particularly preferred embodiments, activation is carried out by adding sodium hydroxide (5M) equivalent to the chlorohydrin content in the resin. The activated resin may then be diluted to 20% solids for application to the pulp. Further, it is contemplated that direct activation could be employed by using sodium carbonate or sodium bicarbonate, versus merely adding the resin to a neutral papermaking system. Additionally, direct activation may produce predominantly epoxide groups from the aminochlorohydrins.
Merely neutralizing the resin much like what would be experienced in a papermaking system generates azetidinium but at a very slow rate. Ideally, it would be desired to pump the resin from a drum into the papermaking system and have it xe2x80x9cactivatexe2x80x9dunder neutral papermaking conditions. Any other bases may be employed as well as a way of activating the resins.
The reduced specific viscosity (RSV) is preferably about 0.139 to about 0.155 dL/g measured in 1.0N NH4Cl at 2.0%. The method employed is based on ASTM D446.
The processes of the invention can be conducted batchwise, continuously or semi-continuously and can be readily so modified by those of ordinary skill in the art.
The invention also comprises methods of increasing the wet strength of cellulosic products by adding the resins of the invention to cellulosic materials to produce wet strengthened cellulosic materials. The resins can be added at the wet end of processes for manufacturing cellulosic products. Procedures for wet strengthening such cellulosic products in which wet strength resins of the invention may be used are well known to those of ordinary skill in the papermaking art, and are disclosed in, for example, U.S. Pat. No. 2,926,154, to KEIM, incorporated by reference above and herein specifically for such disclosure.
The invention also comprises cellulosic products comprising cellulosic fibers and such wet strength resins. The resin component of such components is novel, as is discussed above. Cellulosic products containing cellulosic products and wet strength resins are disclosed in the documents incorporated by reference above, which documents are hereby incorporated by reference as though set forth in full herein.
Methods of the invention also comprise using the resins as creping adhesives. Procedures in which the resins of the invention may be used as creping adhesives are also are well known to those of ordinary skill in the papermaking art.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent.
The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. In the following examples, all temperatures are set forth uncorrected in degrees Celsius; unless otherwise indicated, all parts and percentages are by weight.